Landfill compactors are configured with wheels especially adapted to operate in sanitary land fills or refuse dumps. In that environment the first priority for such equipment is to obtain maximum compaction density of the materials deposited in the landfill thereby maximizing the capacity of the landfill. Typically a landfill compactor vehicle is self propelled and equipped with four large steel wheels. These wheels are each provided with an array of cleats that extend radially from a cylindrical wheel drum. By reason of the high compactor vehicle weight, sometimes amounting to 120,000 pounds (about 54,431 kg), the cleats mounted on the wheel drum apply localized forces to crush, grind and generally aggressively knead the refuse into the landfill mass.
The number of cleats mounted on a given wheel drum has a direct effect upon the aggressiveness of the compaction action and the resultant compaction density in the landfill. Hence a smaller number of cleats on a wheel drum of a given circumference, say 28 to 30 cleats on a 65 inch (1.65 meter) diameter drum, will result in less compaction density than the configuration wherein the wheel drum is equipped with a larger number of cleats, say 45 to 58 cleats. Clearly a larger number of cleats is desirable to achieve higher compaction densities., the compactor wheel sizes being otherwise equal or equivalent. The efficiency gain is apparent from actual observations of the equipment in use on land fill sites.
In an endeavor to minimize entrainment of debris in the region of the compactor vehicle wheel axle assembly, a troublesome problem at land fill sites, the prior art has shown that leaving a cleat free zone or large cleat offset adjacent the inner edge of the compactor wheel, such as by eliminating an entire circumferential row of cleats from the wheel, is generally effective. That arrangement provides about 25% fewer cleats available for aggressive compaction action. Also taught was a trash barrier comprising a circumferential solid or fluted flange mounted at the inner edge of the compactor wheel. This was intended to act as a barrier to reduce wire, cable and trash buildup around the compactor axles. Not uncommonly, the circumferential flange received higher wear that the nearby cleats and needed replacement long before the cleats needed replacement. The foregoing structures are shown in U.S. Pat. No. 5,687,799 issued Nov. 18, 1997 and U.S. Pat. No. 5,769,507 issued Jun. 23, 1998.
Common to both the '799 and '507 patents is that the cleats welded to the wheel drums were all of the same configuration, basically traction affording cleats. Thus, reducing the number of cleats available for trash compaction purposes proportionately reduced the cleats available for traction purposes. The tradeoff for attacking the trash entrainment problem on the wheel axles, as taught by the prior art, was to diminish the traction efficiency of the entire compactor vehicle. The compactor therefore was required to make many more passes over the landfill materials to achieve the intended compaction density. Consequently, higher fuel and operational wear costs were an undesirable result of leaving cleat free zones or a large offset of a cleat row on the compactor wheels.